1. Technical Field
The present invention relates to a composite structure, an aircraft wing and an aircraft fuselage including the composite structure, and a method of manufacturing the composite structure.
2. Background Art
In the areas of aircraft, ships, vehicles, and the like, a composite member made of fiber reinforced plastics (FRP) is widely used as a structure that has high strength and light weight. The composite member has advantages in terms of the fact that the composite member is “lighter and stronger” than metal.
Holes may be formed at this composite member for checking or access at the time of assembly. When holes are formed, strain concentration occurs in peripheral areas of the holes. Even though a strain-concentrated portion reaches fracture strain, metal is finally broken with plastic deformation without being instantly fractured. In a general design, for example, the static strength of a flat plate including holes is evaluated using net stress that is obtained by dividing a load by the cross-sectional area of the flat plate except for the holes. Meanwhile, since the plastic deformation of the composite member is less than the plastic deformation of metal, the sensitivity of the composite member to strain concentration (holes, notches) is high and a strain concentration rate needs to be also considered for the evaluation of the static strength of the composite member. As a result, since the thickness of a peripheral portion of the hole should be increased, advantages in terms of “light weight and high strength” are not achieved.
PTL 1 discloses a hole periphery reinforcing device for reducing a strain concentration rate, which is caused by holes, by providing a portion, which is made of a material having large elongation and low stiffness as compared to a base material, on the peripheral portion of the hole.